Brushholder contact finger



H. F. HARTMAN BRUSHHOLDER CONTACT FINGER Jam.A 12', 1926. 1,569,367

Filed April 2, 1925 A ATTORNEY Patented Jan. 12, 1926.

UNITED `STATES PATENT OFFICE.

HARRY F. HARTMAN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & `MANU'EACTTITEK'IBTGI COMPANY, A CORPORATION- PENNSYL- VANIA.

BRUSHHOLDER CONTACT FINGER.

Application led April 2, 1925. Serial No. 20,072.

holders of thel type shown in the patent to Dobson, No. 1,533,237, granted April 14, 1925, on an application, Serial No. 726,911,

filed July 19, 1924.

In particular, my invention relates to improvements in the finger member of the .brushholder, whereby a material reduction in the cost of manufacture is secured, difculties are successfully overcome in the connection of sheet-metal parts, a renewable brush-engaging tip is provided' of a material having far better wearing qualities than the materials which are vpractical to use for the rest of the linger, and a material .reduction in friction and in -the weight of the moving parts is secured, whereby the light-` pressure action of the spring is more uniform in its application to the brush.

In the laccompanyingdrawing, showing a preferred embodiment of my invention, Fig. 1 is a plan view of thefinger member partly in section on the line I-.-I of Fig. 2, Fig. 2 is an elevational View of the-same.

3 isan enlarged sectional View showing an intermediate stage in the manufacture, Fig. 4 is a sectional view on line IVe-IV 4 vof Fig..2, with the helical Spring and the vratchet wheel assembled with the finger member, and

Fig. 5 is a full-size'elevational view of the complete brushho'lder assembly. In the embodiment .hown i1 the drawing,

a brushholder unit, comprising a brushholder frame 6, is secured, by means of a clamp 7 to the frame 8 of a motor or other 2 dynamo-electric machine. Thebrfushholder 50, .frame 6 carries a brushholder box 9. through which extends the carbonbrush 10 which bears on a commutator member or other current-collecting device l1 of the machine. f Removably mounted in suitable bearings in the biuhhclder frame 6 is a fngensupport- 'ing shaft 12 on which is mounted the brushengaging finger 13 of my improved construction. i

My brushholder lingerO 13 comprises a tubular bearing member 14 surrounding the shaft 12, a separate brush-engaging tip 15 and a separate sheet-metal finger portion 16, the latter having a cup-shaped part 17 and an integral arm extension 18. 'lhe tip `15 is of T-shape and has a leg member .19

which is riveted at20 tothe arm extension 18 of the finger portion, said arln extension being preferably channel-shaped in order to receive the leg of the tip member. i

In the construction illustrated in-the Dobson patent, the entire finger, which I make in the three parts 14, 15, 16, was cast as a single. piece. It has been found that the materials which are suitable for casting are not durable at the contact point between the Atip and the top of the brush, the tip being rapidly eroded away, apparently due to the effect of the poor contact'and sparking at that point. I have made the tip member removable, so that, if it does wear, it may be replaced, and, by making it removable, I have been enabled to make the tip member of more durable material, such as hard drawn copper. This material isl more resistant to the effects of sparking than the sheet brass or other sheet material from which I stamp the finger portion 16.

The cup-shaped part17 of the sheet-metal finger portion 16 has a perforation Yin its closed end, the material of said end being bent'inwardly to form acircular fiange 21 providing a cylindrical seat 22, said seat having as great length, in an axial direction, as is practical. The tubular bearing member 14 has a reduced ,end portion 23 forming a shoulder which is-engaged by said inwardlybent flange 21, as shown in Figj3.

The end of the reduced portion of the tubular member, which thus projects beyond the cup-shaped part 17, is spun over and pounded into place against the closed end of the cup portion, and is subsequently milled. 0E to provide a smooth seat 24`of less area than the closed end of the cup portion, whereby the end thrust friction of the finger member may be materially reduced. In view of the fact that the amount of -force utilized on the linger member is only about three pounds, it will be apparent that the provi- Sion of an eiicent end-thrust bearing surface is a veryy desirable feature in the design of the brush contact finger.

The cup-shaped part 17 and the tubular member 14 provide an annular space which is adapted to house a helical spring 25, as shown in Fig.y 4. One end of the spring is bent at 26 for interlocking engagementwith a perforation 27 which is tapped at an angle into the bottom of the sheet-metal finger portion 16, the location being such as to prevent, as far as possible, the ingress of dirt through said opening. The spring chamber is further closed by means of a split tubular member 28 of thin sheet material which is sprung into place `within the cup-shaped portion 17, thus protecting the spring 25 from exposure at the fopen side of the cup portion where the arm extension 18 is formed. The spring-engaging opening 27 in the finger member is located at the side of the cup portion 17 rather than at the end, as was necessary inthe cast construction shown in the above-mentioned Dobson patent, the end location in the latter being necessitated by reason of the exigencies of the, casting operation.- By my construction, I bring the end 26 of the'spring member out of the side of the cup-shaped hub member, thereby saving space at the end, where the thrust bearing surfaces are provided.

The open end of the annular space comprising the spring-chamber of the finger member is closed by a ratchet 29 which is provided with a perforation 30, for receiving the other end of the spring 25, and a hub 3l, for receiving the shaft 12, as indicated in Fig. 4. The hub 3l bears against the end of the tubular bearing member 14, and a slight clearance vis provided between the ratchet 29 and the open end of the cup-shaped, part 17, as indicated at 32, in order to reduce friction.

The unit comprising the pressure finger 16, with the enclosed spring 25 and the juxtaposed ratchet 29, is assembled between the,

bearing supports of thebrushholder frame 6, and the shaft 12 is inserted throughthe bearings in the brush-holder frame and through the bearings in the tubular member 14 of the finger and in the hub portion 31 of the ratchet. The spring is placed under tension by rotating the ratchet 29, which is held in place by a spring pawl 33 which is carried by the brushholder frame 6, as shown in Fig. 5. The finger member is provided with the usual current-carrying shunt 34 for carrying the current to the frame and preventing the currentfrom passing through the spring 25.-

From the foregoing description, it will be seen that I have provided an improved design wherein the several benefits enumerated hereinbefore arev secured., While I have illustrated my invention in the form at present preferred, I do not intendl that the aparm extension, the closed end of said cupshaped part having an inwardly bent circular flange forming a cylindrical seat, said tubular member having a reduced end portion constituting a shoulder engaged by said inwardly bent flange, the reduced end portion of said tubular member being riveted over the closed end of said cup-shaped part, a helical spring mounted around said tubular member within said cup-shaped part and having, its inner end detachably -secured therein, a tension-adjusting member mounted on said shaft against the open end of said cup-shaped part for totally enclosing said spring and retaining the outer end there'of, and means for holding said tension-adjust ing member in a fixed langular position for maintaining said pressiue finger under stress.

2. A brushholder for electrical machines comprising a brushholder frame having a brush box and a removably mounted shaft, a laterally extending pressure finger extending over the brush box and adapted to engage the top of the brush, said pressure finger having a tubular bearing member for said shaft, a separate brush-engaging `tip and a separate sheet-metal finger portion having a cup-shaped part and an arm extension, said tip having a leg member fastened to the arm extension of said finger portion and being of a material more resistant to sparking at the brush contact than the material of'sa-id finger portion, the closed end of said cup-shaped part having a perforation the rim portion of which is rigidly united to said tubular bearing member, a helical spring mounted around said tubular member within said cup-shaped part and having its inner end dctachably secured therein, a tension-adjusting member mounted on said shaft against the open end of said cup-shaped part for totally enclosing said spring and retaining the' outer cud thereof, and means for holding said tension-adjusting member in a fixed angular position for maintaining said pressure f iger under stress.

3. A brushholder for electrical machines comprising a finger-supporting shaft and characterized by a finger having a hub portion on said shaft and adapted to yieldably press a brush into" operative engagement with a 'co-operating current-collecting deioA 'metal finger portion ,having a cup-shaped vice7 saidinger comprising an arm exteneiing -from said hub portion, and a sepafate "lla-Shaped tip for contacting With'the brush, and means for securing the ieg of the tip to said arm, the material of sai tip being more resistant to sparking at the brush contact than the material of said arm.

4. An article of manufacture comprising a tubular member and a separate sheetpart and an arm extension, the closed end; o

seid @ap-e apeii pant having' an inwaidiy bent, eiicinaf flange oming a cyiinoiioai seat, said tubular member havin@ a reduced enfi portion constituting; a shoui er engaged by said inwardly bent iia'nge, the reduced end portion of said tubular member being ivetee. ovei1 the dosed end' of Said eupshaped pait,

Tin testimony whereof, i have hereunto subscribed my name this 31st day of Maioln 1925.

HARRY F. MARTE/IAN. 

